what are some digital cable upgrades/servers?

I just installed a Qsonix music server into my system. My system has: Meridian G-68 processor; G-98 DVD/CD player; MBL 111e's mains; Aerial CC5 center; MBL 8011's monoblock main amps; Sunfire 7x400 for center; rears; zone 2. Harmonic Tech speaker cables; ps power cords and Shanatu;
At first I had Qsonix configured for analog out into Meridian; sounded horrible; changed to digital output of server into Meridian; and it sang great. I am using stock digital cord that came with unit. Has anyone found a great digital cord to connect server to processor that has a noticable improvement; that costs less than $500? what about it helped improve sound stage and detail? Other brands auditioned? My music tastes are eclectic; jazz; vocals; pop/rock; classical. By the way; the Qsonix with its touch screen has been fantastic; easy to set up and easy to use; wife likes it...sounds almost as good as native system...
Thanks for your suggestions...
Are you referring to TOSLink, S/PDIF (Coaxial) or AES/EBU?

I've auditioned Meridian gear before; their gear excels at digital, I am not surprised you found their native inputs and outputs were superior to your ears.

Reasonable cost digital cables I've used with great results;

TOSLink: Audiquest Optilink-5
S/PDIF: Audioquest EagleEye (still have 2 of these)
AES/EBU: Audioquest Raven

All can be found on Agon under $500.

From what I've heard the mid-level Tara digital cables are
also amazing. I auditioned a 0.8 digital and was impressed
but wound up going with a pair of Tara 0.5 AES/EBU cables
between my transport and DAC with amazing results. That
stated, the 0.5 retails for considerably higher than $500.

If you start with the list above and solicit other opinions,
you'll be at a very good starting point.
75 ohm digital cable with rca pin...not toslink. I have to admit my ignorance; don't know difference between s/pdif; and aes/ebu; please explain what this terminology means; and differences... I'm looking at the Harmonic digital magic II; lists for $500; can find on the 'gon for $300; but the eagle eye also caught my eye....I appreciate your response and help.
75-ohm with RCA pin is S/PDIF; I'm no expert so I cannot tell you the diffs at the cable/specification level.

I've listened to the Harmonic and several other 75-ohm cables before; in your price range,
I'd suggest the Eagle Eye. You'll be amazed at the musicality, imaging, etc...you get from it.
Bottom-line, to me, it doesn't sound like a digital cable.
I am one of the owners of Qsonix if you use a good dac the digital cable becomes less important. I can reccomend some dacs if you need some help